This invention relates to percutaneous transluminal coronary angioplasty (PTCA), and more particularly to angioplasty using balloon catheters in which the balloon allows perfusion in its inflated condition.
Coronary angioplasty is a widely used alternative to open-heart coronary bypass surgery for the treatment of acute and chronic heart problems. A major contributing factor in such heart problems is a reduction in nutrient blood flow to the muscles of the heart resulting from a reduction of blood flow through the coronary blood vessels. The reduction in flow may be caused by deposits of atherosclerotic plaque on the walls of the affected blood vessel, which causes a narrowing of the lumen or channel of the blood vessel. When the lumen is sufficiently narrowed, the rate of blood flow therethrough may be so diminished that spontaneous formation of a thrombus or clot occurs by a variety of physiologic mechanisms. Once a blood clot has begun to form, it extends within minutes into the surrounding blood, as mentioned in U.S. Pat. No. 4,643,186, issued Feb. 17, 1987, in the names of Rosen and Walinsky. The presence of atherosclerotic plaque not only reduces the blood flow to the muscles of the heart but is a major predisposing factor in coronary thrombosis.
The art relating to angioplasty includes many advances, such as the microwave-aided angioplasty described in the above-mentioned Rosen and Walinsky patent, reduced diameters as described in an article entitled "The Balloon On A Wire Device" by Myler et al, published at pages 135-140 of Volume 14, No. 2, 1988 of the periodical "Catheterization and Cardiovascular Diagnosis," published by Alan R. Liss, and various configurations of guide wires and catheter lumens, described for example in "Selection or Dilatation Hardware for PCTA-1985" by Topol et al., published at pages 629-637 of Volume 11, No. 6, 1985 of the aforementioned periodical.
In general, an angioplasty procedure is performed by obtaining access to the interior of the affected coronary artery, and advancing a deflated balloon to the location of the stenosis. The balloon is inflated by applying fluid pressure through an inflation/deflation ("inflation") lumen of the catheter, to thereby apply balloon pressure tending to expand the lumen of the coronary artery. When the stenotic portion of the lumen of the blood vessel or coronary artery has about the same diameter as adjacent portions which are free from plaque, the procedure may be terminated, the balloon deflated and the catheter removed. It has been observed, as in the article entitled "Perfusion During Coronary Angioplasty," by Rossen, published at pages 103-106 in the June 1989 issue of Cardio, that increased time with the balloon inflated is associated with an improved result.
Those portions of the heart muscle supplied with blood flow through the artery are partially deprived of blood flow when the catheter with deflated balloon is being positioned in the stenotic region, and may be completely deprived of blood flow when the balloon is inflated. This in turn has a tendency to decrease heart pumping efficiency, and the blood pressure tends to drop. Chest pains result in some patients. Either of these indications may undesirably require early termination of the procedure. Dilatation catheters are available, as mentioned in the above-mentioned Rossen article, in which perfusion or blood flow past the occluding catheter and balloon is provided by fenestrations or apertures into the distal lumen of the catheter on both sides of the balloon. When the distal lumen is also used for a guide wire, the guide wire must be retracted during perfusion, which requires additional manipulation, and may result in loss of position of the balloon. Further manipulation is required if the guide catheter surrounding the dilatation catheter must also be retracted. Such perfusion catheters tend to be somewhat larger in diameter and stiffer than conventional catheters having the same inflated balloon diameter, and are therefore more difficult to position. Also, their larger diameter excludes their use in the small arteries into which conventional balloon catheters may fit. It should also be noted that similar perfusion catheters without balloons may be used as a temporary or emergency measure until corrective surgery can be performed in cases of total occlusion.